Control device and medical imaging system

ABSTRACT

There is provided a control device including: an autofocus control section configured to execute an autofocus operation by moving at least one optical member; and an autofocus operation determination section configured to determine whether it is possible for the autofocus operation to bring biological tissue into focus, the biological tissue serving as an object. In a case where the autofocus operation determination section determines that it is not possible for the autofocus operation to bring the object into focus, the autofocus control section moves the at least one optical member to a predicted focal position set in advance in accordance with a purpose of imaging to make it possible to further improve convenience of a user.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of and is based upon andclaims the benefit of priority under 35 U.S.C. § 120 from U.S. Ser. No.15/564,928, filed Oct. 6, 2017, herein incorporated by reference, whichis a National Stage Application of International Application No.PCT/JP2016/063931, filed May 10, 2016. The present document alsoincorporates by reference the entire contents of Japanese prioritydocument, 2015-100962 filed in Japan on May 18, 2015.

TECHNICAL FIELD

The present disclosure relates to a control device and a medical imagingsystem.

BACKGROUND

Endoscopic systems or microscopic systems (which will be genericallyreferred to as imaging systems) are known as systems that imagebiological tissue of patients to allow the biological tissue to beobserved at the time of surgical operations or inspections. Some of theimaging systems have autofocus (AF) functions of automatically bringingobjects into focus. For example, Patent Literature 1 discloses amicroscopic system that detects a light amount change in the light froman object, drive an optical system to execute an AF operation in a casewhere the light amount change falls within a predetermined range, andmoves the optical system to an initial position without performing anyAF operation in a case where the light amount change is beyond thepredetermined range.

CITATION LIST Patent Literature

Patent Literature 1: JP H5-232378A

DISCLOSURE OF INVENTION Technical Problem

The technology described in Patent Literature 1, however, simply movesthe optical system to the initial position in a case where the lightamount change is beyond the predetermined range, namely in a case whereit is determined that it is not possible to normally execute an AFoperation. As a result, there is a high probability that an unclearimage out of focus is acquired. To carry out surgical operations orinspections, a surgeon thus needs an additional operation such asmanually adjusting the position of the optical system for focusing. Inview of the above-described circumstances, an imaging system isrequested that is more convenient for users.

The present disclosure then proposes a novel and improved control deviceand medical imaging system that can further improve the convenience of auser.

Solution to Problem

According to the present disclosure, there is provided a control deviceincluding: an autofocus control section configured to execute anautofocus operation by moving at least one optical member; and anautofocus operation determination section configured to determinewhether it is possible for the autofocus operation to bring biologicaltissue into focus, the biological tissue serving as an object. In a casewhere the autofocus operation determination section determines that itis not possible for the autofocus operation to bring the object intofocus, the autofocus control section moves the at least one opticalmember to a predicted focal position set in advance in accordance with apurpose of imaging.

Further, according to the present disclosure, there is provided amedical imaging system including: an image sensor configured to imagebiological tissue serving as an object; an optical system configured toconcentrate light from the object on the image sensor, and configured ina manner that at least one optical member is movable on an optical axisfor a focusing operation; an autofocus control section configured toexecute an autofocus operation by moving the at least one opticalmember; and an autofocus operation determination section configured todetermine whether it is possible for the autofocus operation to bringthe object into focus. In a case where the autofocus operationdetermination section determines that it is not possible for theautofocus operation to bring the object into focus, the autofocuscontrol section moves the at least one optical member to a predictedfocal position set in advance in accordance with a purpose of imaging.

According to the present disclosure, in a case where it is determinedthrough that it is not possible for an autofocus operation to bring anobject into focus, at least one optical member (such as a focus lens)moved in the autofocus operation moves to a predicted focal position setin advance in accordance with the purpose of imaging. The position ofthe at least one optical member at which an object comes into focus inan object distance assumed in accordance with the purpose of imaging canbe set as the predicted focal position on the basis of the objectdistance. The movement of the at least one optical member to thepredicted focal position thus offers an image that has biological tissueserving as an object relatively in focus. A surgeon can therefore carryout a surgical operation or an inspection with no additional operationsuch as focusing, which can further improve the convenience of thesurgeon.

Advantageous Effects of Invention

As described above, according to the present disclosure, it is possibleto improve the convenience of a user. Note that the effects describedabove are not necessarily limitative. With or in the place of the aboveeffects, there may be achieved any one of the effects described in thisspecification or other effects that may be grasped from thisspecification.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating a configuration example of animaging system according to the present embodiment.

FIG. 2 is an explanatory diagram for describing a concept of an AFoperation in a contrast method.

FIG. 3 is an explanatory diagram for describing the concept of the AFoperation in the contrast method.

FIG. 4 is a flowchart illustrating an example of a procedure of animaging method according to the present embodiment.

FIG. 5 is an explanatory diagram for describing a concept of an AFoperation in a phase difference method.

FIG. 6 is an explanatory diagram for describing the concept of the AFoperation in the phase difference method.

MODE(S) FOR CARRYING OUT THE INVENTION

Hereinafter, (a) preferred embodiment(s) of the present disclosure willbe described in detail with reference to the appended drawings. In thisspecification and the appended drawings, structural elements that havesubstantially the same function and structure are denoted with the samereference numerals, and repeated explanation of these structuralelements is omitted.

Hereinafter, the description will be made in the following order.

-   1. Configuration of Imaging System-   2. Imaging Method-   3. Modifications-   3-1. Case Where Phase Difference Method is Used-   3-2. Case Where Depth Map Method is Used-   3-3. Case Where Triangulation Method is Used-   4. Supplemental Information

Additionally, the following describes, as a surgeon, a user who performsa variety of operations on an imaging system according to an embodimentof the present disclosure for the sake of convenience. The descriptiondoes not, however, limit users who use the imaging system. A variety ofoperations on the imaging system may be executed by any user such asanother medical staff member.

(1. Configuration of Imaging System)

The configuration of an imaging system according to an embodiment of thepresent disclosure will be described with reference to FIG. 1. FIG. 1 isa block diagram illustrating a configuration example of the imagingsystem according to the present embodiment.

FIG. 1 illustrates that an imaging system 1 according to the presentembodiment includes an imaging device 10, and a control device 20 thatperforms various kinds of signal processing for the operation of theimaging device 10. The imaging system 1 is a medical imaging system 1,and has an objective of imaging the biological tissue of a patient atthe time of a surgical operation or an inspection in the presentembodiment. The imaging system 1 can be, for example, an endoscopicsystem or a microscopic system. An endoscope inserted into a body cavityof a patient images the biological tissue of the body cavity at the timeof a surgical operation or an inspection in the endoscopic system.Meanwhile, an operative site is imaged by a microscopic section(including, for example, an optical system and an image sensor in alens-barrel) supported above the operative site by a support arm or thelike at the time of laparotomy or craniotomy in the microscopic system.A surgeon can carry out a surgical operation or an inspection whilereferring to an operative site or an inspection part imaged by anendoscopic section or the microscopic section.

FIG. 1 illustrates the configuration corresponding to the endoscopicsystem as an example of the imaging system 1. For example, the imagingdevice 10 corresponds to a camera head, and the control device 20corresponds to a camera control unit (CCU). The imaging device 10 isconnected to the control device 20 by an optical fiber and/or anelectrical signal cable. Various kinds of information can be transmittedand received through an optical signal and/or an electrical signal.

Additionally, FIG. 1 chiefly illustrates only components necessary fordescribing the present embodiment, but illustrates no other components.The imaging system 1 can, however, include various components of atypical endoscopic system such as an endoscope and a light source devicethat supplies the endoscope with illumination light with whichbiological tissue of a patient serving as an object is irradiated at thetime of imaging.

An insertion section of the endoscope which is small in diameter isinserted into a body cavity of a patient at the time of imaging. Thedistal end of the insertion section of the endoscope is provided with anillumination window. An object is irradiated with illumination lightsupplied from the light source device through the illumination window.The distal end of the insertion section of the endoscope is alsoprovided with an observation window through which reflected light(observation light) acquired by the illumination light being reflectedfrom the object is acquired. The observation light acquired through theobservation window is guided to the proximal end of the endoscope by alight guide member provided in the lens-barrel of the endoscope. Theimaging device 10 (i.e., camera head) is attached to the proximal end ofthe endoscope. Observation light is collected by an image sensor 105discussed below which is provided in the imaging device 10, therebycapturing an object image.

The following describes the configurations of the imaging device 10 andthe control device 20 in more detail. First, the configuration of theimaging device 10 will be described.

The imaging device 10 includes an optical system 101 and the imagesensor 105. Further, the imaging device 10 includes a zoom lens drivingsection 107, a focus lens driving section 111, and an image sensordriving section 115 as functions thereof.

The optical system 101 concentrates, on the image sensor 105, theobservation light guided through the endoscope. The optical system 101includes a zoom lens 102 and a focus lens 103. Additionally, FIG. 1representatively illustrates only the zoom lens 102 and the focus lens103, but the optical system 101 may also include a variety of opticalmembers such as another lens and filter. The type and number of opticalmembers included in the optical system 101, the optical property of eachoptical member, and the like are adjusted as needed in a manner that theoptical system 101 forms an object image on the light receiving surfaceof the image sensor 105.

The zoom lens 102 is a lens for adjusting the magnification of theoptical system 101. The zoom lens 102 is configured to be movable on theoptical axis. The position of the zoom lens 102 on the optical axis iscontrolled, thereby adjusting the magnification of the optical system101. Additionally, the zoom lens 102 is an example of optical membersfor adjusting the magnification of the optical system 101. As long asthe position of at least one optical member included in the opticalsystem 101 on the optical axis is adjusted, and the magnification of theoptical system 101 is hereby adjusted, the number and type of opticalmembers configured to be movable for adjusting the magnification are notlimited in the present embodiment.

The focus lens 103 is a lens for adjusting the focal distance of theoptical system 101. The focus lens 103 is configured to be movable onthe optical axis. The position of the focus lens 103 on the optical axisis controlled, thereby adjusting the focal distance of the opticalsystem 101. Additionally, the focus lens 103 is an example of opticalmembers for adjusting the focal distance of the optical system 101. Aslong as the position of at least one optical member included in theoptical system 101 on the optical axis is adjusted, and the focaldistance of the optical system 101 is hereby adjusted, the number andtype of optical members configured to be movable for adjusting the focaldistance are not limited in the present embodiment.

The image sensor 105 images an object by receiving observation light onthe light receiving surface thereof. Specifically, the image sensor 105has a light receiving surface on which light receiving elements such asphotodiodes are arranged. The image sensor 105 receives observationlight on the light receiving surface, thereby acquiring an electricalsignal corresponding to the observation light through photoelectricconversion, namely an imaging signal that is an electrical signalcorresponding to an object image. The configuration of the image sensor105 is not limited. A variety of known image sensors such as a chargecoupled device (CCD) image sensor and a complementarymetal-oxide-semiconductor (CMOS) image sensor may be used as the imagesensor 105. The imaging signal acquired by the image sensor 105 istransmitted to an imaging signal processing section 117 of the controldevice 20 which will be described below.

The zoom lens driving section 107 includes, for example, a motor, adriver circuit that supplies a drive current to the motor, and the like.The zoom lens driving section 107 moves the zoom lens 102 along theoptical axis. The operation of the zoom lens driving section 107 iscontrolled by a zoom lens drive control section that is not illustrated.The zoom lens drive control section includes a variety of processorssuch as a central processing unit (CPU) and a digital signal processor(DSP), or a microcomputer or the like in which the processor and astorage element such as a memory are both installed. The zoom lens drivecontrol section controls the operation of the zoom lens driving section107. The zoom lens drive control section may also include a variety ofintegrated circuits such as a field-programmable gate array (FPGA), adriver integrated circuit (IC), and/or a dedicated large-scaleintegration (LSI) (i.e., application specific integrated circuit(ASIC)). The function of the zoom lens drive control section can beimplemented by the processor included in the zoom lens drive controlsection executing operational processing in accordance with apredetermined program.

Specifically, the zoom lens drive control section controls the drivingof the zoom lens driving section 107 in accordance with the movementamount of the zoom lens 102 calculated by a zoom operation controlsection 127 of the control device 20 which will be described below,thereby moving the zoom lens 102 by the movement amount to adjust themagnification of the optical system 101. Additionally, in a case wherean optical member other than the zoom lens 102 is also configured to bemovable for adjusting the magnification of the optical system 101, thezoom lens driving section 107 may also move the other optical member onthe optical axis under the control of the zoom lens drive controlsection.

Additionally, the configurations and functions of the zoom lens drivingsection 107 and the zoom lens drive control section may be similar tothe configuration and function of a mechanism installed in a typicalimaging device (such as a camera head of an endoscopic system) forimplementing the zoom function. The configurations and functions of thezoom lens driving section 107 and the zoom lens drive control sectionwill not be thus described in detail here.

The focus lens driving section 111 includes, for example, a motor, adriver circuit that supplies a drive current to the motor, and the like.The focus lens driving section 111 moves the focus lens 103 along theoptical axis. The operation of the focus lens driving section 111 iscontrolled by a focus lens drive control section that is notillustrated. The focus lens drive control section includes a variety ofprocessors such as a CPU and a DSP, a microcomputer, and the like. Thefocus lens drive control section controls the operation of the focuslens driving section 111. The focus lens drive control section may alsoinclude a variety of integrated circuits such as a FPGA, a driver IC,and/or a dedicated LSI (i.e., ASIC). The function of the focus lensdrive control section can be implemented by the processor included inthe focus lens drive control section executing operational processing inaccordance with a predetermined program.

Specifically, the imaging system 1 has an autofocus (AF) function. Thefocus lens drive control section controls the driving of the focus lensdriving section 111 in accordance with the movement amount of the focuslens 103 calculated by an autofocus control section 118 (AF controlsection 118) of the control device 20 described below in accordance witha predetermined AF method, thereby moving the focus lens 103 by themovement amount to adjust the focal distance of the optical system 101.Additionally, in a case where an optical member other than the focuslens 103 is also configured to be movable for adjusting the focaldistance of the optical system 101, the focus lens driving section 111may also move the other optical member on the optical axis under thecontrol of the focus lens drive control section.

Additionally, the configurations and functions of the focus lens drivingsection 111 and the focus lens drive control section may be similar tothe configuration and function of a mechanism installed in a typicalimaging device (such as a camera head of an endoscopic device) forimplementing the AF function. The configurations and functions of thefocus lens driving section 111 and the focus lens drive control sectionwill not be thus described in detail here.

The image sensor driving section 115 corresponding to a driver fordriving the image sensor 105. The image sensor driving section 115supplies a driving signal (signal for driving a transistor or the likeinstalled in the image sensor 105) to the image sensor 105 atpredetermined timing, thereby causing the image sensor 105 to execute anoperation such as an imaging operation or a reset operation atpredetermined timing and acquire an imaging signal corresponding to anobject image. Additionally, although not illustrated, an image sensordrive control section that controls the operation of the image sensordriving section 115 can be provided to the imaging device 10 or thecontrol device 20. The image sensor drive control section includes avariety of processors such as a CPU and a DSP, a microcomputer, and thelike. The image sensor drive control section instructs the image sensordriving section 115 about the timing at which the driving signal issupplied to the image sensor 105, thereby controlling the driving of theimage sensor 105 via the image sensor driving section 115. Additionally,the function of the image sensor drive control section can beimplemented by the processor included in the image sensor drive controlsection executing operational processing in accordance with apredetermined program.

The start and end of imaging can be controlled in accordance with aninstruction issued by a surgeon via an input device such as a switch(not illustrated) in the imaging system 1. Specifically, the imagingsystem 1 includes an input device for receiving an instruction signalindicating the start of imaging. The image sensor drive control sectioncontrols the driving of the image sensor 105 in accordance with aninstruction issued by a surgeon via the input device, and imaging can behereby started and ended.

Additionally, the configurations and functions of the image sensordriving section 115 and the image sensor drive control section may besimilar to the configuration and function of a mechanism installed in atypical imaging device (such as a camera head of an endoscopic device)for implementing the imaging function of the image sensor for imaging anobject. The configurations and functions of the image sensor drivingsection 115 and the image sensor drive control section will not be thusdescribed in detail here.

Additionally, the components corresponding to the above-described zoomlens drive control section, focus lens drive control section, and/orimage sensor drive control section may be installed in the imagingdevice 10 or the control device 20. Further, although not illustrated,the control device 20 can include a connector (not illustrated) to whichan optical fiber and/or an electrical signal cable used to exchangevarious kinds of information with the imaging device 10 is connected.The connector may be configured in a manner that an integrated circuitwhich executes various kinds of information processing can be installedin the connector. The components corresponding to the above-describedzoom lens drive control section, focus lens drive control section,and/or image sensor drive control section may be installed in theconnector.

The configuration of the imaging device 10 has been described above. Theconfiguration of the imaging device 10 is not, however, limited to thisexample. The imaging device 10 includes at least the image sensor 105,and the optical system 101 for concentrating observation light on theimage sensor 105, and at least one optical member included in theoptical system 101 only has to be configured to be drivable for the AFfunction in the present embodiment. The imaging device 10 may have anyspecific device configuration. Various known kinds of configuration maybe applied as the imaging device 10.

Next, the configuration of the control device 20 will be described. Thecontrol device 20 includes the imaging signal processing section 117,the AF control section 118, an AF operation determination section 125,and the zoom operation control section 127 as functions thereof.

The control device 20 corresponds to, for example, a CCU as describedabove. The control device 20 includes a variety of processors and astorage element such as a memory. Each of the above-described functionsof the control device 20 is implemented by a processor included in thecontrol device 20 executing operational processing in accordance with apredetermined program.

The zoom operation control section 127 performs various kinds of controlfor the zoom operation of the imaging system 1. Specifically, theimaging system 1 can receive an instruction signal (zoom instructionsignal) that is issued by a surgeon and indicates that a zoom operationis performed. The zoom instruction signal is input via a variety ofinput devices such as a switch that are included in the imaging system1, but not illustrated. The zoom instruction signal also includes aninstruction about magnification. The zoom operation control section 127decides the movement amount of the zoom lens 102 which can offer theinstructed magnification on the basis of the zoom instruction signal.Information on the decided movement amount is transmitted to the zoomlens drive control section that is not illustrated. The zoom lens drivecontrol section moves the zoom lens 102 via the zoom lens drivingsection 107 by the decided movement amount, thereby adjusting themagnification of the optical system 101 in accordance with theinstruction of the surgeon. Additionally, in a case where an opticalmember other than the zoom lens 102 is also configured to be movable foradjusting the magnification of the optical system 101, the zoomoperation control section 127 may also decide the movement amount of theother optical member on the optical axis.

Additionally, the function of the zoom operation control section 127 maybe similar to the function of a typical existing imaging system foradjusting magnification. Accordingly, the function of the zoom operationcontrol section 127 will not be described in more detail here.

The imaging signal processing section 117 performs various kinds ofsignal processing such as a gamma correction process and a white balanceadjustment process on an imaging signal acquired by the image sensor 105for allowing a display device (not illustrated) to display an objectimage. The imaging signal (which will be referred to as image signal)subjected to the various signal processing performed by the imagingsignal processing section 117 is transmitted to the display device. Thedisplay device shows an image of the object on the basis of the imagesignal. A surgeon can observe the condition of the biological tissueserving as the object via the display device. Further, the imagingsignal processing section 117 also provides the image signal to an AFframe decision section 119 of the AF control section 118 which will bedescribed below.

The AF control section 118 performs various kinds of control for the AFoperation of the imaging device 10. FIG. 1 illustrates, as an example,the functional components of the AF control section 118 which correspondto a case where the AF method is a contrast method. The contrast methodis a method in which a focusing operation is performed by searching for,while moving at least one optical member (focus lens 103 in theillustrated example) included in the optical system 101, the position ofthe optical member at which the contrast of an object image ismaximized, and moving the optical member to the position at which thecontrast is maximized.

The AF method applied to the imaging system 1 is not, however, limitedin the present embodiment. A variety of known methods may be used as theAF method. An AF method of a passive type can be, however, favorablyapplied to the imaging system 1 in the present embodiment.

Here, AF methods are roughly categorized into two types in general: anactive type; and a passive type. A method of the active type is a methodin which the distance to an object is measured by irradiating theobject, for example, with near infrared light or the like and receivingthe reflected light thereof, and a focusing operation is performed bymoving an optical member included in the optical system on the basis ofthe measured distance in a manner that the object comes into focus.Meanwhile, a method of the passive type is a method in which a focusingoperation is performed by radiating no light or the like for measuringdistance from the optical system, but moving an optical member includedin the optical system on the basis of information acquired from acaptured object image in a manner that an object comes into focus.

As described above, the imaging system 1 can be, for example, anendoscopic system. It is, however, difficult for the endoscopic systemto adopt the active type as the AF method. This is because the activetype requires the endoscope to include a component for measuringdistance at the proximal end, which increases the size of the proximalend of the endoscope, and can place a heavier burden on the body of apatient. Even in a case where the imaging system 1 is a microscopicsystem, it is not preferable to increase the size of the configurationof the microscopic section which images an operative site in order tosecure a surgeon a working space. The passive type can be thus appliedfavorably as the AF method of the imaging system 1 in the presentembodiment.

A variety of methods referred to as phase difference method, depth mapmethod, and triangulation method in general are known in addition to theabove-described contrast method as AF methods of the passive type. Thesemethods all perform a focusing operation on the basis of informationacquired from a captured object image. However, these methods have thecharacteristic that, in a case where the contrast of the object image isrelatively low (in a case of so-called low contrast), it is difficult tonormally perform a focusing operation (i.e., it is difficult for an AFoperation to bring an object into focus). Such an AF method in which itis difficult to normally perform a focusing operation in a case where anobject image has low contrast can also be considered a method in whichan AF operation is executed on the basis of contrast. Accordingly, thefollowing description also refers to such an AF method as method basedon contrast for the sake of convenience. Many of the AF methods of thepassive type are methods based on contrast. Accordingly, it can also besaid that the present embodiment targets the imaging system 1 to which amethod based on contrast is applied as the AF method.

FIG. 1 will be referred to again, and the function of the AF controlsection 118 will be continuously described. The AF control section 118includes the AF frame decision section 119, a contrast detection section121, and a focus lens movement amount decision section 123 as functionsthereof. Additionally, the AF control section 118 executes a series ofprocesses for an AF operation in accordance with an instruction signal(AF instruction signal) which is input by a surgeon and indicates thatthe AF operation is performed. The AF instruction signal can be inputvia a variety of input devices such as a switch that are included in theimaging system 1, but not illustrated.

The AF frame decision section 119 generates an object image on the basisof an image signal acquired by the imaging signal processing section117, and decides, from the object image, an area (AF frame) that comesinto focus when an AF operation is performed. The AF frame decisionsection 119 provides information on the decided AF frame to the contrastdetection section 121.

The contrast detection section 121 detects the contrast of the areacorresponding to the AF frame decided by the AF frame decision section119 in the object image. The AF control section 118 regards the contrastof the area corresponding to the AF frame as the contrast of the objectimage, and performs an AF operation. The contrast detection section 121provides information on the detected contrast of the area correspondingto the AF frame (i.e., contrast of the object image) to the focus lensmovement amount decision section 123.

The focus lens movement amount decision section 123 decides the movementamount of the focus lens 103 on the basis of the information on thedetected contrast of the object image by the contrast detection section121. Specifically, the focus lens movement amount decision section 123decides the movement amount of the focus lens 103 on the basis of thecontrast of the object image in the last step and the contrast of theobject image in the present step in a manner that the focus lens 103moves by a predetermined distance on the optical axis in the directionin which the contrast is higher. Additionally, the movement amount ofthe focus lens 103 only has to be decided in the first step (in a casewhere there is no information on the contrast of the object image in thelast step) in a manner that the focus lens 103 is moved by apredetermined distance in a predetermined direction set in advance.

Information on the decided movement amount of the focus lens 103 istransmitted to the focus lens drive control section that is notillustrated. The focus lens drive control section moves the focus lens103 via the focus lens driving section 111 by the decided movementamount.

The series of processes described above will be repeatedly executedbelow, thereby executing an AF operation in the contrast method. Thatis, the imaging signal processing section 117 generates an image signalon the basis of an imaging signal acquired by the image sensor 105 afterthe focus lens 103 moves. The AF frame decision section 119, thecontrast detection section 121, and the focus lens movement amountdecision section 123 execute the above-described processes again on thebasis of the image signal, and the focus lens 103 is moved by the focuslens drive control section in accordance with the decided movementamount. The repeated execution of these processes finally moves thefocus lens 103 to the position at which the contrast of the object imageis maximized. An image that has the object in focus is acquired, and theseries of processes for the AF operation is then terminated.

Additionally, in a case where an optical member other than the focuslens 103 is also configured to be movable for adjusting the focaldistance of the optical system 101, the focus lens movement amountdecision section 123 may also decide the movement amount of the otheroptical member on the optical axis.

Further, the series of processes (process of deciding the AF frame,process of detecting the contrast, and process of deciding the movementamount of the focus lens 103) described above and performed by the AFcontrol section 118 may be similar to the series of processes performedin an AF operation in the typical existing contrast method. A variety ofknown methods used for an AF operation in the contrast method may beused as a specific method for each process, and will not be describedhere in detail. For example, JP 2748637B, which is a prior applicationfiled by the Applicants of the present application, can be seen for thedetails of an AF operation in the contrast method in detail.

Here, in a case where a method based on the contrast of an object imagelike the contrast method is applied to the imaging system 1 as the AFmethod, there is the probability that an AF operation is not normallyperformed by the AF control section 118 when an object having lowcontrast is imaged.

FIGS. 2 and 3 are explanatory diagrams each of which describes theconcept of the AF operation in the contrast method. FIG. 2 illustratesan example of the contrast of an object image in a case where an AFoperation can be normally executed in the contrast method. Asillustrated in FIG. 2, in a case of an object that undergoes arelatively big change in contrast, the position of the focus lens 103can be relatively easily found out at which the contrast is maximized.An AF operation can be therefore normally executed. Meanwhile, asillustrated in FIG. 3, in a case of an object that undergoes arelatively small change in contrast, it is difficult to find out theposition of the focus lens 103 at which the contrast is maximized. Thereis the probability that an AF operation is not normally performed.

Here, it is assumed in general that biological tissue of a patient suchas blood, internal organs, and bones is imaged in the medical imagingsystem. These kinds of biological tissue have, however, low contrast inmany cases. In a case where an AF operation is performed in a methodbased on contrast, it can be difficult to normally perform the AFoperation. For example, a subtle increase or decrease in contract causedby noise or the like can cause an optical member such as a focus lens tomove to a wrong position that is not the original focal position.Alternatively, in a case where the contrast method is used, there is theprobability that it is difficult to carry out a surgical operation or aninspection because it is not possible to decide the position (i.e.,focal position) at which the contrast is maximized, but an opticalmember such as a focus lens keeps on moving on the optical axis. In thisway, failure in normally executing an AF operation in the imaging systemcan considerably stress a surgeon.

In view of such circumstances, for example, Patent Literature 1discloses, as existing technology, a microscopic system that has the AFfunction, and stops, in a case where it is determined that it is notpossible to normally execute an AF operation, the AF operation, andmoves an optical system to an initial position. The technology describedin Patent Literature 1, however, returns the optical system to theinitial position in a case where it is determined that it is notpossible to normally execute an AF operation. As a result, there is ahigh probability that an image out of focus is acquired. To carry out asurgical operation or an inspection, a surgeon thus needs manualfocusing. It cannot be therefore said that the system which is alwaysconvenient for a surgeon has been built.

The AF operation determination section 125 then determines in thepresent embodiment whether it is possible to normally execute an AFoperation, namely whether it is possible for an AF operation to bring anobject into focus. In a case where it is determined that it is notpossible for an AF operation to bring an object into focus, the processfor the AF operation in the AF control section 118 is then stopped, andthe focus lens 103 is moved to a predetermined position set in advancein accordance with the purpose of imaging. Here, the position of thefocus lens 103 at which an object comes into focus in an object distanceassumed in accordance with the purpose of imaging can be set on thebasis of the object distance as the predetermined position. There isthus a high probability that an image acquired after the focus lens 103moves to the position is an image that has biological tissue serving asan object in focus. The following description also refers to thepredetermined position set in advance in accordance with the purpose ofimaging as predicted focal position.

In this way, according to the present embodiment, in a case where it isdifficult to normally perform an AF operation, the focus lens 103 movesto a predicted focal position, thereby acquiring a clear image that hasbiological tissue serving as an object in better focus. A surgeon canthus carry out a surgical operation or an inspection with no additionaloperation such as focusing. According to the present embodiment, theimaging system 1 that is more convenient can be therefore provided.

An AF operation determination process performed by the AF operationdetermination section 125, and the following process in the imagingsystem 1 will be described in more detail. As described above, the AFoperation determination section 125 determines whether it is possible tonormally execute an AF operation, namely whether it is possible for anAF operation to bring an object into focus (whether it is possible todecide the position of the focus lens 103 at which an AF operationbrings an object into focus). Additionally, the AF operationdetermination process performed by the AF operation determinationsection 125 can be executed as needed at predetermined intervals whilean AF operation is being executed.

In a case where the contrast method is applied like the illustratedconfiguration example, for example, the AF operation determinationsection 125 can determine that it is not possible to for an AF operationto bring an object into focus in a case where a predetermined timeelapses in the AF operation without deciding the final position of thefocus lens 103 (i.e., position of the focus lens 103 at which thecontrast of an object image is maximized). Further, for example, in acase where the focus lens 103 arrives a predetermined number of times atan end point of the movable range thereof in an AF operation, the AFoperation determination section 125 can determine that it is notpossible for the AF operation to bring an object into focus.Alternatively, these determination criteria may be combined and used.That is, in a case where a predetermined time elapses without decidingthe position of the focus lens 103 at which the contrast of an objectimage is maximized, or in a case where the focus lens 103 arrives apredetermined number of times at an end point of the movable rangethereof in an AF operation, the AF operation determination section 125may determine that it is not possible for the AF operation to bring anobject into focus.

Additionally, values that can be used in general for the AF operationdetermination process may be applied as appropriate as the predeterminedtime and the predetermined number of times. The predetermined time canbe, for example, approximately five seconds. Further, the predeterminednumber of times can be, for example, one time at each end point.Further, the AF operation determination section 125 uses, as adetermination criterion of an AF operation, whether the focus lens 103arrives a predetermined number of times at an end point of the movablerange thereof in the AF operation in the above-described example, butmay also use, as the determination criterion, whether the focus lens 103arrives a predetermined number of times at an end point of a specificrange included in the movable range thereof in the AF operation. Thatis, the AF operation determination section 125 may determine whether itis possible to normally execute an AF operation, in accordance withwhether the focus lens 103 moves within a part of the movable rangethereof in the AF operation without finding out an appropriate focalposition.

For example, the AF operation determination section 125 can be providedwith information on the decided movement amount of the focus lens 103and information indicating whether an AF operation is terminated fromthe focus lens movement amount decision section 123. The AF operationdetermination section 125 can execute an AF operation determinationprocess as described above on the basis of these kinds of information.

The criterion of the AF operation determination process performed by theAF operation determination section 125 is not however, limited to thisexample. A variety of known determination criteria used in general foran AF operation in the contrast method may be used in the presentembodiment as a criterion for determining whether it is possible tonormally execute an AF operation.

Additionally, in a case where another method is applied as the AF methodin the imaging system 1, the AF operation determination section 125 maydetermine as needed whether it is possible to normally execute an AFoperation in the method corresponding to the applied AF method. Avariety of methods are known in general as a method for determiningwhether it is possible to normally execute an AF operation. For example,a variety of methods for determining that an object has so-called lowcontrast are proposed for a variety of existing imaging devices to whicha method based on contrast is applied as the AF method. The AF operationdetermination section 125 may perform a determination process in avariety of known methods on the basis of the applied AF method.

In a case where the AF operation determination section 125 determinesthat it is possible for an AF operation to bring an object into focus,the AF control section 118 continues the series of processes describedabove for the AF operation, namely continues the AF operation.

Meanwhile, in a case where the AF operation determination section 125determines that it is not possible for an AF operation to bring anobject into focus, the AF operation determination section 125 providesinformation indicating that to the focus lens movement amount decisionsection 123. In this case, the process for the AF operation in the AFcontrol section 118 is stopped. The focus lens movement amount decisionsection 123 decides the movement amount of the focus lens 103 so as tomove the focus lens 103 to the predicted focal position, and moves thefocus lens 103 in accordance with the movement amount via the focus lensdrive control section (not illustrated) and the focus lens drivingsection 111.

As described above, the position of the focus lens 103 at which anobject comes into focus in an object distance assumed in accordance withthe purpose of imaging can be set as the predicted focal position on thebasis of the object distance. The movement of the focus lens 103 to thepredicted focal position thus offers an image that has biological tissueserving as an object relatively in focus.

Additionally, the “purpose of imaging” can include a surgical procedure,a clinical department, a preference of a surgeon, and the like. Once thesurgical procedure and/or the clinical department is decided, it can bepredicted with a high probability in what object distance and what kindof biological tissue is observed. Accordingly, setting the predictedfocal position on the basis of the surgical procedure and/or theclinical department makes it possible to set a more appropriate positionas the predicted focal position. Further, even in a case where the samebiological tissue is observed, the optimum object distance can differ inaccordance with preferences of a surgeon. Setting the predicted focalposition in accordance with a surgeon who uses the imaging system 1 toobserve an operative site can thus build the imaging system 1 that ismore convenient for the surgeon.

Further, the predicted focal position may also be set in accordance withthe optical property of the optical system attached to the imagingdevice 10. For example, it is assumed that a different type of endoscopeis attached and used in the imaging system 1 in accordance with thepurpose of imaging (surgical procedure or the like). In general, anobject distance recommended to be used for the endoscope is set inaccordance with the type thereof, namely the optical system of theendoscope, in many cases. When the predicted focal position is set, thepredicted focal position may be thus set in on the basis of the type ofendoscope attached to the imaging device 10 to bring an object intofocus in consideration of the object distance that can be set inaccordance with the optical system of the endoscope. Additionally, thereis another optical system in between in addition to the endoscope, thepredicted focal position may also be set in consideration of the opticalproperty of the other optical system. Alternatively, in a case where theimaging system 1 is a microscopic system, and an additional opticalsystem is attached to the microscopic section that can correspond to theimaging device 10, the predicted focal position may also be set inaccordance with the optical property of the additional optical system.

Additionally, the predicted focal position may be manually set by asurgeon before a surgical operation in accordance with factors (such asa surgical procedure, a clinical department, a preference of thesurgeon, and the optical system of the endoscope) as described abovewhich can decide the predicted focal position. Alternatively, forexample, in a case where the predicted focal position can be set inaccordance with the type of endoscope, the imaging system 1 may have afunction of detecting the type of the attached endoscope. In addition,the predicted focal position may be automatically set in accordance withthe type of endoscope on the basis of a detection result of thedetection function.

The configuration of the imaging system 1 according to the presentembodiment has been described above with reference to FIG. 1.Additionally, the configuration illustrated in FIG. 1 is merely anexample. The imaging system 1 may have any specific device configurationas long as the imaging system 1 can execute the above-describedprocesses as a whole. For example, the control device 20 may have someof the functions of the imaging device 10 in FIG. 1. Conversely, theimaging device 10 may have some of the functions of the control device20.

Alternatively, the functions corresponding to the respective blocksillustrated in FIG. 1 may be distributed in more devices, or a singledevice may have all of the functions. For example, FIG. 1 illustratesthe configuration corresponding to an endoscopic system as an example ofthe imaging system 1, but the imaging system 1 may also be a microscopicsystem in the present embodiment. In a case where the imaging system 1is a microscopic system, the illustrated components can be all installedin a single device to constitute the imaging system 1.

Further, it is possible to manufacture a computer program for executingthe functions of the imaging system 1 according to the presentembodiment as described above, and implement the manufactured computerprogram in an information processing device such as a personal computer(PC). Further, there can also be provided a computer-readable recordingmedium having such a computer program stored therein. Examples of therecording medium include a magnetic disk, an optical disc, amagneto-optical disk, and a flash memory. The computer program may alsobe distributed via a network, for example, using no recording medium.

(2. Imaging Method)

A procedure of an imaging method executed by the above-described imagingsystem 1 will be described with reference to FIG. 4. FIG. 4 is aflowchart illustrating an example of the procedure of the imaging methodaccording to the present embodiment.

Additionally, a process characteristic of the present embodiment in thefocusing operation process for bringing an object into focus is executedamong the series of processes for imaging the object in the imagingmethod according to the present embodiment. FIG. 4 thus illustrates aprocedure of the focusing operation process among the series ofprocesses in the imaging method according to the present embodiment. Theseries of processes illustrated in FIG. 4 are processes that can beexecuted, for example, in a case where a surgeon inputs an AFinstruction signal.

Additionally, the series of processes illustrated in FIG. 4 are actuallyexecuted in the imaging system 1 while an image signal is beingacquired. An image that has an object in focus is hereby acquired. Thatis, a process of acquiring an image signal on the basis of an imagingsignal (corresponding to the process executed by the imaging signalprocessing section 117 illustrated in FIG. 1) is executed before theprocess in step S101 illustrated in FIG. 4.

FIG. 4 illustrates that, for example, the input of the AF instructionsignal first serves as a trigger and an AF operation is executed in thefocusing operation process in the imaging method according to thepresent embodiment (step S101). For example, in a case where thecontrast method is applied, a process of searching for, while moving thefocus lens 103, the position of the focus lens 103 at which the contrastof an object image is maximized is executed in step S103. The processcorresponds to the processes executed by the AF control section 118illustrated in FIG. 1, the focus lens drive control section (notillustrated), and the focus lens driving section 111. The presentembodiment is not, however, limited to this example. In step S103, an AFoperation based on other various types of AF methods may be executed.

Next, it is determined in the AF operation whether it is possible tonormally execute the AF operation, namely whether it is possible for theAF operation to bring an object into focus (step S103). Specifically, instep S103, it can be determined whether it is possible for the AFoperation to bring an object into focus in the method corresponding tothe method of the AF operation executed in step S101.

For example, in a case where the contrast method is applied, it isdetermined in step S103 that it is not possible for the AF operation tobring the object into focus, in a case where a predetermined timeelapses without deciding the position of the focus lens 103 at which thecontrast of the object image is maximized in the AF operation, or in acase where the focus lens 103 arrives at a predetermined number of timesat an end point of the movable range thereof in the AF operation. In theother cases, it is determined that it is possible for the AF operationto bring the object into focus.

The present embodiment is not, however, limited to this example. In stepS103, a process of determining whether it is possible to execute an AFoperation performed in general in a variety of AF methods may beexecuted. Additionally, the process in step S103 corresponds to theprocess executed by the AF operation determination section 125illustrated in FIG. 1.

The determination process in step S103 can be executed as needed atpredetermined intervals in the AF operation. In a case where it isdetermined in step S103 that it is possible for the AF operation tobring the object into focus, the processing returns to step S101 and theAF operation is continued. It is then determined again in step S103after predetermined intervals whether it is possible for the AFoperation to bring the object into focus. In a case where the AFoperation is normally terminated while the processes in step S101 andstep S103 are being repeatedly executed, namely in a case where theobject accurately comes into focus, the series of processes in theimaging method according to the present embodiment are also terminated.

Meanwhile, in a case where it is determined in step S103 that it is notpossible for the AF operation to bring the object into focus, theprocessing proceeds to step S105. In step S105, the focus lens 103 ismoved to a predetermined position (predicted focal position) set inadvance in accordance with the purpose of imaging. The position of theat focus lens 103 at which an object comes into focus in an objectdistance assumed in accordance with the purpose of imaging can be set asthe predicted focal position on the basis of the object distance.Additionally, the process illustrated in step S105 corresponds to theprocesses executed by the focus lens movement amount decision section123 illustrated in FIG. 1, the focus lens drive control section (notillustrated), and the focus lens driving section 111.

Once the focus lens 103 is moved in step S105 to the predicted focalposition, the series of processes in the imaging method according to thepresent embodiment are terminated. In this way, in a case where it isdetermined that it is not possible to normally execute an AF operation,the focus lens 103 is moved to the predicted focal position. This makesit possible to acquire a clear image that is relatively in focus withoutrequiring an additional operation of a surgeon for focusing. Inaddition, it is possible to improve the convenience of the surgeon.

The procedure of the imaging method according to the present embodimenthas been described with reference to FIG. 4.

(3. Modifications)

Some modifications of the above-described embodiment will be described.Additionally, each of the modifications described below corresponds tothe above-described embodiment in which the AF method is changed.

(3-1. Case Where Phase Difference Method is Used)

A case where a phase difference method is used as the AF method in theimaging system 1 illustrated in FIG. 1 will be described. The phasedifference method is a method in which a focusing operation is performedby calculating the distance to an object on the basis of the imageinterval between two object images acquired by causing observation lightto form images at different positions in the light receiving surface,and moving the focus lens 103 on the basis of the calculated distance tothe object to bring the object into focus.

FIGS. 5 and 6 are explanatory diagrams each of which describes theconcept of the AF operation in the phase difference method. FIG. 5illustrates an example of the contrast of an object image in a casewhere an AF operation can be normally executed in the phase differencemethod. As illustrated in FIG. 5, in a case of an object havingrelatively high contrast, it is possible to relatively clearly detectthe image interval between two object images. Accordingly, it ispossible to calculate the distance to the object on the basis of theimage interval, and execute an AF operation.

Meanwhile, as illustrated in FIG. 6, in a case of an object havingrelatively low contrast, it is difficult to acquire the relationshipbetween two object images and detect the image interval between the twoobject images. It is therefore not possible to calculate the distance tothe object. In addition, there is the probability that an AF operationis not normally performed.

In this way, similarly to the above-described embodiment, there is theprobability that it is not possible to normally execute an AF operationon an object having low contrast in the phase difference method. In acase where the phase difference method is used, the imaging system thatis convenient for a surgeon can be thus built by configuring the imagingsystem in a manner that the focus lens is moved to the predicted focalposition in a case where it is determined that it is not possible for anAF operation to bring an object into focus.

The imaging system to which the phase difference method is applied asthe AF method corresponds to the configuration of the imaging system 1illustrated in FIG. 1 in which the function of the AF control section118 for an AF operation and the determination criterion of the AFoperation determination section 125 are changed. Specifically, forexample, the AF control section 118 illustrated in FIG. 1 executes, asprocesses for an AF operation, a process of acquiring the image intervalbetween two object images, a process of calculating the distance to anobject on the basis of the image interval, and a process of calculating,on the basis of the calculated distance to the object, the movementamount of the focus lens 103 to the position at which the object comesinto focus in the imaging system to which the phase difference method isapplied. Further, for example, the AF operation determination section125 determines whether it is possible for an AF operation to bring anobject into focus in a variety of methods used in general for an AFoperation in the phase difference method.

Additionally, in a case where the phase difference method is used, theremay be provided another image sensor for measuring distance in theimaging device 10 in addition to the image sensor 105 for imaging. Inaddition, an AF operation may also be performed on the basis of twoobject images acquired by the other image sensor. Alternatively, an areafor measuring distance may be secured in a part of the light receivingsurface of the image sensor 105, and an AF operation may be performed onthe basis of two object images acquired on the light receiving surfacecorresponding to the area for measuring distance. In this case, thesingle image sensor 105 can both image an object and measure distancefor an AF operation. Accordingly, it is possible to further simplify theconfiguration of the imaging device 10.

(3-2. Case Where Depth Map Method is Used)

A case where a so-called depth map method is used as the AF method inthe imaging system 1 illustrated in FIG. 1 will be described. The depthmap method is an AF method that uses space recognition technology, andis a method in which a focusing operation is performed by calculatingthe distance to an object on the basis of the blurring degree (defocusdegree) of an object image and moving the focus lens 103 on the basis ofthe calculated distance to the object in a manner that the object comesinto focus.

Here, it is known that it is difficult to accurately detect the defocusdegree for an object having low contrast. That is, similarly to theabove-described embodiment, there is the probability that it is notpossible to normally execute an AF operation on an object having lowcontrast in the depth map method. In a case where the depth map methodis used, the imaging system that is convenient for a surgeon can be thusbuilt by configuring the imaging system in a manner that the focus lensis moved to the predicted focal position in a case where it isdetermined that it is not possible for an AF operation to bring anobject into focus.

The imaging system to which the depth map method is applied as the AFmethod corresponds to the configuration of the imaging system 1illustrated in FIG. 1 in which the function of the AF control section118 for an AF operation and the determination criterion of the AFoperation determination section 125 are changed. Specifically, forexample, the AF control section 118 illustrated in FIG. 1 executes, asprocesses for an AF operation, a process of detecting the defocus degreeof an object image, a process of calculating the distance to an objecton the basis of the detected defocus degree of the object image, and aprocess of calculating, on the basis of the calculated distance to theobject, the movement amount of the focus lens 103 to the position atwhich the object comes into focus in the imaging system to which thedepth map method is applied. Further, for example, the AF operationdetermination section 125 determines whether it is possible for an AFoperation to bring an object into focus in a variety of methods used ingeneral for an AF operation in the depth map method.

(3-3. Case Where Triangulation Method is Used)

A case where a so-called triangulation method is used as the AF methodin the imaging system 1 illustrated in FIG. 1 will be described. Thetriangulation method is an AF method in which 3D stereogram technologyis used, and a focusing operation is performed by calculating thedistance to an object in accordance with the principle of triangulationon the basis of the disparity information acquired from two objectimages acquired by causing observation light to form images at differentpositions in the light receiving surface, and moving the focus lens 103on the basis of the calculated distance to the object to bring theobject into focus.

Here, it is difficult to acquire the relationship between two objectimages for an object having low contrast and accurately acquiredisparity information. That is, similarly to the above-describedembodiment, there is the probability that it is not possible to normallyexecute an AF operation on an object having low contrast in thetriangulation method. In a case where the triangulation method is used,the imaging system that is convenient for a surgeon can be thus built byconfiguring the imaging system in a manner that the focus lens is movedto the predicted focal position in a case where it is determined that itis not possible for an AF operation to bring an object into focus.

The imaging system to which the triangulation method is applied as theAF method corresponds to the configuration of the imaging system 1illustrated in FIG. 1 in which the function of the AF control section118 for an AF operation and the determination criterion of the AFoperation determination section 125 are changed. Specifically, forexample, the AF control section 118 illustrated in FIG. 1 executes, asprocesses for an AF operation, a process of acquiring disparityinformation from two object images, a process of calculating thedistance to an object on the basis of the principle of triangulation onthe basis of the disparity information and the baseline distance(distance between the light receiving elements corresponding to thepositions at which the two object images are formed), and a process ofcalculating, on the basis of the calculated distance to the object, themovement amount of the focus lens 103 to the position at which theobject comes into focus in the imaging system to which the triangulationmethod is applied. Further, for example, the AF operation determinationsection 125 determines whether it is possible for an AF operation tobring an object into focus in a variety of methods used in general foran AF operation in the triangulation method.

Additionally, in a case where the triangulation method is used, theremay be provided another image sensor for measuring distance in theimaging device 10 in addition to the image sensor 105 for imaging. Inaddition, an AF operation may also be performed on the basis of twoobject images acquired by the other image sensor. Alternatively, an areafor measuring distance may be secured in a part of the light receivingsurface of the image sensor 105, and an AF operation may be performed onthe basis of two object images acquired on the light receiving surfacecorresponding to the area for measuring distance. In this case, thesingle image sensor 105 can both image an object and measure distancefor an AF operation. Accordingly, it is possible to further simplify theconfiguration of the imaging device 10.

(4. Supplemental Information)

The preferred embodiment(s) of the present disclosure has/have beendescribed above with reference to the accompanying drawings, whilst thepresent disclosure is not limited to the above examples. A personskilled in the art may find various alterations and modifications withinthe scope of the appended claims, and it should be understood that theywill naturally come under the technical scope of the present disclosure.

Further, the effects described in this specification are merelyillustrative or exemplified effects, and are not limitative. That is,with or in the place of the above effects, the technology according tothe present disclosure may achieve other effects that are clear to thoseskilled in the art from the description of this specification.

Additionally, the present technology may also be configured as below.

(1)

A control device including:

an autofocus control section configured to execute an autofocusoperation by moving at least one optical member; and

an autofocus operation determination section configured to determinewhether it is possible for the autofocus operation to bring biologicaltissue into focus, the biological tissue serving as an object, in which

in a case where the autofocus operation determination section determinesthat it is not possible for the autofocus operation to bring the objectinto focus, the autofocus control section moves the at least one opticalmember to a predicted focal position set in advance in accordance with apurpose of imaging.

(2)

The control device according to (1), in which

the predicted focal position is set in accordance with a surgicalprocedure of a surgical operation in which the object is imaged.

(3)

The control device according to (1) or (2), in which

the predicted focal position is set in accordance with a clinicaldepartment in which the object is imaged.

(4)

The control device according to any one of (1) to (3), in which

it is possible to set the predicted focal position in accordance with asurgeon who observes the object that is imaged.

(5)

The control device according to any one of (1) to (4), in which

the predicted focal position is set in accordance with an opticalproperty of an optical system attached to an imaging device that isconnected to the control device.

(6)

The control device according to any one of (1) to (5), in which

the autofocus operation is executed on the basis of contrast of anobject image.

(7)

The control device according to (6), in which

the autofocus operation is an operation of focusing by searching for,while moving the at least one optical member, a position at which thecontrast of the object image is maximized, and moving the at least oneoptical member to the position at which the contrast is maximized.

(8)

The control device according to (7), in which

in a case where a predetermined time elapses in the autofocus operationwithout deciding the position of the at least one optical member atwhich the contrast of the object image is maximized, it is determinedthat it is not possible for the autofocus operation to bring the objectinto focus, and the at least one optical member moves to the predictedfocal position.

(9)

The control device according to (7) or (8), in which

in a case where the at least one optical member arrives a predeterminednumber of times at an end point of a specific range included in amovable range in the autofocus operation, it is determined that it isnot possible for the autofocus operation to bring the object into focus,and the at least one optical member moves to the predicted focalposition.

(10)

The control device according to (6), in which

the autofocus operation is an operation of focusing by calculating adistance to the object on the basis of an image interval between twoobject images acquired by causing light from the object to form imagesat different positions in a light receiving surface, and moving the atleast one optical member on the basis of the distance.

(11)

The control device according to (6), in which

the autofocus operation is an operation of focusing by calculating adistance to the object on the basis of a defocus degree of the objectimage, and moving the at least one optical member on the basis of thedistance.

(12)

The control device according to (6), in which

the autofocus operation is an operation of focusing by calculating adistance to the object in accordance with a principle of triangulationon the basis of disparity information acquired from two object imagesacquired by causing light from the object to form images at differentpositions in a light receiving surface, and moving the at least oneoptical member on the basis of the distance.

(13)

A medical imaging system including:

an image sensor configured to image biological tissue serving as anobject;

an optical system configured to concentrate light from the object on theimage sensor, and configured in a manner that at least one opticalmember is movable on an optical axis for a focusing operation;

an autofocus control section configured to execute an autofocusoperation by moving the at least one optical member; and

an autofocus operation determination section configured to determinewhether it is possible for the autofocus operation to bring the objectinto focus, in which

in a case where the autofocus operation determination section determinesthat it is not possible for the autofocus operation to bring the objectinto focus, the autofocus control section moves the at least one opticalmember to a predicted focal position set in advance in accordance with apurpose of imaging.

REFERENCE SIGNS LIST

-   1 imaging system-   10 imaging device-   20 control device-   101 optical system-   102 zoom lens-   103 focus lens-   105 image sensor-   107 zoom lens driving section-   111 focus lens driving section-   115 image sensor driving section-   117 imaging signal processing section-   118 AF control section-   119 AF frame decision section-   121 contrast detection section-   123 focus lens movement amount decision section-   125 AF operation determination section-   127 zoom operation control section

The invention claimed is:
 1. A medical imaging system comprising:processing circuitry configured to obtain a medical image from a medicalimaging device, evaluate an area of the medical image for focusadjustment, determine, when the evaluation of the area satisfies apredetermined condition, a movement amount of an at least one focus lensbased on the evaluation of the area, and determine, when the evaluationof the area does not satisfy the predetermined condition, the movementamount of the at least one focus lens based on a predetermined position,wherein the predetermined position is a memorized position in a memory,the memorized position in the memory being different from an initialposition of the focus lens.
 2. The medical imaging system according toclaim 1, wherein the processing circuitry is further configured toevaluate the area by at least one of a contrast detection method, aphase difference method, a depth map method, or a triangulation method.3. The medical imaging system according to claim 1, wherein theprocessing circuitry is further configured to determine thepredetermined position based on an optical system for generating themedical image.
 4. The medical imaging system according to claim 1,wherein the medical imaging device is an endoscope, and thepredetermined position is based on a type of the endoscope.
 5. Themedical imaging system according to claim 1, wherein the medical imagingdevice is a microscope, and the predetermined position is based on anoptical system of the microscope.
 6. The medical imaging systemaccording to claim 1, wherein the evaluation of the area producescontrast information based on the medical image.
 7. The medical imagingsystem according to claim 1, wherein the predetermined condition iswhether the area of the medical image is determined, based on theevaluation of the area, to be a focus adjustable before a predeterminedtime elapses.
 8. The medical imaging system according to claim 1,wherein the predetermined condition is whether the area of the medicalimage is determined, based on the evaluation of the area, to be focusadjustable before the at least one focus lens arrives a predeterminednumber of times at an end point of a specific range included in amovable range.
 9. The medical imaging system according to claim 7,wherein the evaluation of the area is based on contrast information ofthe medical image, and the processing circuitry is further configured todetermine, based on the evaluation of the area, the area is focusadjustable when the position at which the contrast is maximum issearched.
 10. The medical imaging system according to claim 8, whereinthe evaluation of the area is based on contrast information of themedical image, and the processing circuitry is further configured todetermine, based on the evaluation of the area, the area is focusadjustable when the position at which the contrast is maximum issearched.
 11. The medical imaging system according to claim 1, whereinthe predetermined position is determined in accordance with an opticalproperty of an optical system attached to the medical imaging device.12. The medical imaging system according to claim 1, wherein the focusadjustment is an autofocus operation.
 13. The medical imaging systemaccording to claim 3, wherein the memory stores at least one memorizedposition in accordance with the optical system, and the processingcircuitry is further configured to detect the optical system anddetermine the predetermined position in accordance with the opticalsystem.
 14. An endoscope system comprising: an endoscope including anoptical property of an optical system; and processing circuitryconfigured to obtain an endoscope image from the endoscope, evaluate anarea of the endoscope image for focus adjustment, determine, when theevaluation of the area satisfies a predetermined condition, a movementamount of an optical member of the endoscope based on the evaluation ofthe area, and determine, when the evaluation of the area does notsatisfy the predetermined condition, the movement amount of the opticalmember based on a predetermined position, wherein the predeterminedposition is a memorized position in a memory, the memorized positionbeing determined based on a type of the endoscope.
 15. The endoscopesystem according to claim 14, wherein the predetermined position isdetermined based on the optical property of the optical system.
 16. Theendoscope system according to claim 14, wherein the memorized positionin the memory is one of a plurality of memorized positions in accordancewith the type of the endoscope, and the processing circuitry is furtherconfigured to detect the type of the endoscope and determine thepredetermined position in accordance with the type of the endoscope. 17.A medical imaging method, comprising: obtaining, by processingcircuitry, a medical image from a medical imaging device, evaluating, bythe processing circuitry, an area of the medical image for focusadjustment, determining, by the processing circuitry and when theevaluation of the area satisfies a predetermined condition, a movementamount of a focus lens based on the evaluation of the area, determining,by the processing circuitry and when the evaluation does not satisfy thepredetermined condition, the movement amount of the focus lens based ona predetermined position not based on the evaluation of the area,wherein the predetermined position is a memorized position in a memory,the memorized position being determined based on a type of the medicalimaging device.
 18. The endoscope system according to claim 14, whereinthe evaluation of the area produces contrast information based on theendoscope image.
 19. The endoscope system according to claim 14, whereinthe evaluation of the area is based on contrast information of themedical image, and the processing circuitry is further configured todetermine, based on the evaluation of the area, the area is focusadjustable when the position at which the contrast is maximum issearched.
 20. The endoscope system according to claim 14, wherein thefocus adjustment is an autofocus operation.